Notes on Practical Skills in Physics II

Graphing Data

• Identify Variables:
  • Independent Variable: on X-axis (horizontal), left in data table.
  • Dependent Variable: on Y-axis (vertical), right in data table.
• Variable Range: Subtract lowest from highest data value.
• Graph Scale: Spread graph to fit space.
• Label Axes: Clearly indicate data.
• Plot Data Points: Mark with dots, label if clear.
• Draw Graph: Use curve/line of best fit, not "connect-the-dots".
• Title Graph: Clearly describe graph purpose.

Scientific Graphs

• Extrapolation: Extending graph beyond data.
• Interpolation: Predicting between data points.
• Graphs usually line graphs with best-fit lines.

Accuracy and Precision

• Accuracy: Closeness to true value (e.g., 75.95g for 100.00g standard is inaccurate).
• Precision: Closeness of measurements to each other.
• High precision but low accuracy often due to faulty instruments.

Errors in Calculated Quantities

• Uncertainty Types:
  1. Random Uncertainties: Unpredictable variations, reduced by repeated measures.
  2. Systematic Errors: Constant discrepancies, need redesign or theoretical analysis.
  3. Personal Errors: Poor technique or bias.
• Resolution: Smallest measurable interval.
• Mistakes: Scale misreading or equipment fault.
• Anomalous Points: Outliers due to measurement mistakes.
• Uncertainty Measures: Absolute and relative uncertainty.
• Percentage Uncertainty: Difference from accepted value over accepted value, expressed as percentage.

Uncertainties in Derived Quantities

• Operations:
  • Multiply/Divide: Sum of percentage uncertainties.
  • Add/Subtract: Sum maximum probable uncertainties.
• Examples: Calculating with lengths, volumes, periods.

Measurement Techniques

• Estimating Uncertainty:
  • Use spread of repeat readings or resolution of device.
  • For single readings, use smallest division of instrument.

Graph Analysis

• Use Graphs to Assess Accuracy: Compare experimental values with known values using uncertainty.

Equipment and Measurement

• Sensitivity: Output per unit input.
• Reliability: Consistency in repeated measures.
• Validity: Measurement relevance.
• Repeatability: Same operator and method.
• Reproducibility: Different operators and apparatus.

Apparatus Handling

• Metre Rule, Masses, Thermometers, Oscillations: Specific handling and resolution guidelines.
• Data Loggers: Advantages and disadvantages in various scenarios.
• Geiger-Muller Tube: Use in detecting radioactivity, errors due to dead time.

Experiments and Applications

• Specific Heat Capacity, Pendulum, Hooke's Law, Circuits: Setups and calculations.
• Graphical Methods and Error Reduction: Use of graphs for linear relationships and minimizing error.
• Safety Precautions: Across experiments to ensure safety.

These notes summarize key concepts and methodologies for practical skills in physics, emphasizing data handling, error analysis, and experimental techniques. They provide a reference for understanding how to measure and interpret physical quantities accurately.